Sorry, I was thinking in another thread.
Now, if your processor is an i7-9xx series, with 6GB (3x2GB) in tri-channel is enough.
If your computer isn't a i7-9xx series, I mean, an i5-750 or i7-860, with 4GB (2x2GB) in dual channel is good for now.
Also, a x64 OS is necessary for use 4GB or more.